Target Audience:
Owners, DIY mechanics, and professional technicians working on the Yamaha TTR90.
Motorcycle Segment:
Entry-level youth motocross/off-road motorcycle.
Key Competitors:
Honda CRF70, Suzuki DR-Z70, Kawasaki KX65 (though KX65 is often geared towards more experienced youth riders).
Manual Purpose:
To provide comprehensive guidance for the maintenance, repair, and troubleshooting of the 2002 Yamaha TTR90.
Value Proposition:
Empowers owners to perform their own maintenance and repairs, saving costs and ensuring optimal performance and longevity of the TTR90.
Engine System:
Engine overhaul, top-end rebuild, piston, rings, cylinder, valve train, crankshaft, connecting rod, oil pump, lubrication system.
Fuel System:
Carburetor assembly, disassembly, cleaning, adjustment, fuel tank, fuel lines, fuel filter.
Ignition System:
CDI unit, ignition coil, spark plug, wiring, timing.
Transmission System:
Clutch operation, gear shifting mechanism, gearbox disassembly and reassembly, lubrication.
Electrical System:
Wiring diagrams, battery, charging system, lighting, starter motor (if applicable), kill switch.
Chassis System:
Frame inspection and repair, suspension (front forks, rear shock), steering system, wheel bearings.
Braking System:
Front and rear brake mechanisms (drum brakes), brake cable adjustment, lining inspection.
Bodywork And Fittings:
Seat removal, fuel tank removal, plastics, fenders, handlebar assembly.
Routine Maintenance:
Oil changes, filter replacement, spark plug service, chain adjustment, air filter cleaning/replacement.
Troubleshooting:
Diagnostic procedures for common starting, running, and performance issues.
Engine Repair:
Complete engine rebuild procedures, component replacement, torque specifications.
Carburetor Tuning:
Detailed steps for cleaning, rebuilding, and adjusting the carburetor for optimal performance.
Suspension Service:
Fork oil replacement, seal replacement, shock absorber inspection.
Electrical Diagnostics:
Tracing electrical faults using wiring diagrams, testing components.
Diagnostic Capabilities:
Advanced diagnostics, including component testing and symptom-based troubleshooting.
Rebuild Procedures:
Comprehensive procedures for full engine, transmission, and suspension rebuilds.
Specifications Accuracy:
Includes critical torque values, clearances, fluid capacities, and tolerances for all components.
Engine Type:
Four-stroke, SOHC, Air-cooled
Displacement:
88cc (5.37 cu. in.)
Bore X Stroke:
Approx. 50.0 mm x 45.2 mm (2.0 in x 1.8 in)
Compression Ratio:
Approx. 9.5:1
Valve Clearance Intake:
0.04 - 0.08 mm (0.0016 - 0.0031 in)
Valve Clearance Exhaust:
0.07 - 0.11 mm (0.0028 - 0.0043 in)
Horsepower:
Estimated 6-7 HP (at the crankshaft, actual figures vary)
Torque:
Estimated 4-5 lb-ft (at the crankshaft, actual figures vary)
Carburetor Model:
Likely a Mikuni VM17SS or similar
Fuel Type:
Unleaded gasoline
Fuel Tank Capacity:
Approx. 1.0 L (0.26 US gal)
Fuel Filter:
Inline fuel filter (part number dependent on revision)
Transmission Type:
Automatic (Centrifugal clutch with 3-speed gearbox)
Gear Ratios:
Specific ratios will be detailed in the manual, typically around 2.700 for 1st, 1.750 for 2nd, 1.333 for 3rd.
Clutch Type:
Automatic centrifugal clutch
Transmission Oil Type:
Yamalube 4 (or equivalent SAE 10W-30 API SE Type SC or SB)
Transmission Oil Capacity:
Approx. 0.8 L (0.85 US qt)
Engine Oil Change:
Every 1000 km (600 miles) or 6 months, whichever comes first (refer to manual for exact intervals).
Spark Plug Check:
Every 1000 km (600 miles) or annually.
Air Filter Cleaning:
Every 500 km (300 miles) or more frequently in dusty conditions.
Chain Lubrication Adjustment:
Every 500 km (300 miles) or as needed.
Engine Oil Grade:
Yamalube 4 (or equivalent SAE 10W-30 API SE Type SC or SB)
Brake Fluid:
Drum brakes; typically no user-serviceable hydraulic fluid, relies on cable lubrication/adjustment.
Fork Oil Type:
Yamaha Fork Oil G10 or equivalent (specific viscosity will be in manual, likely around 10W)
Fork Oil Quantity:
Approx. 100 ml per fork leg (check manual for exact specification).
Carburetor Clogging:
Common in small displacement engines left with fuel sitting, leading to hard starting or poor running. Regular cleaning and stabilizer use recommended.
Throttle Cable Wear:
Can stretch or fray over time, requiring adjustment or replacement for smooth throttle operation.
Suspension Seals:
Fork seals can degrade over time, leading to oil leaks. The manual will detail replacement procedures.
Yamaha Motorsports Legacy:
Yamaha has a long-standing and successful history in motorsports, particularly in off-road and motocross, known for reliable and performance-oriented machines.
Ttr Series Development:
The TTR series was developed to offer accessible and user-friendly off-road riding experiences for younger riders, building on Yamaha's motocross expertise.
Manufacturing Location:
Likely assembled in Japan or Southeast Asia, reflecting Yamaha's global manufacturing footprint.
Production Run Years:
The TTR90 was produced for several years, with the 2002 model being an early iteration.
